How To Adjust for Low Distortion

[Digitizer]

In order to get minimal distortions caused by misalignment of object and image planes, the following procedure gives best results:

1. Point the camera to where the negative is going to be
2. Put a mirror in place of the negative
3. Adjust camera and backlight so that the image of the lens is centered in the shot. Adjusting is easier with LiveView and with mirrorless cameras.

In this shot, the lens is not centered vertically. Horizontal offset is minimal.

In this shot, the lens is centered vertically, horizontal position has shifted.
For perfect alignment, repeat step 3 until satisfied.

For better repeatability, you want a rigid setup and a remote trigger.

[nate]

+1 for this. This is a great trick. I’ve tried all kinds of 3d levels, and this is better.

[Digitizer]

Thanks, Nate.

I fiddled some more to make the rig less elastic and got this alignment after a few minutes:

This is my current setup:

The camera sits on a Novoflex macro rail. The copy stand is a Fujimoto “Lucky Enlarger 90M-D” with its head removed. As we can see, I had to put in a shim in order to align the object and image planes. The shim is simply a piece of paper that I folded as many times as was needed to get the alignment. Later, I put the shim under the arca plate, which makes the setup look nicer (nerd alert ;-))

The macro rail allows me to copy 4.5x6 negatives as well as smaller formats without having to move the whole assembly. The mask on the light panel is a temporary model made from cardboard. For easier operations, I plan to make a similar thing from plywood so that I’ll get some distance between the backlight and the negative, which makes the setup a little bit less sensitive to dust.

[brandon]

In my experience, you should actually be focusing the lens in the mirror so you can see the aperture. If you stop the lens down, point a light source at the mirror, and then focus the lens until you can see the aperture, you’ll have a much easier time determining where the center is. This is also helpful if you stop down to the aperture you intend to use for scanning. It’s much easier to put a crosshair over the small aperture opening.